This invention relates generally to exhaust back pressure reducers for internal combustion engines, and more particularly to such a reducer for the engine of a truck tractor for pulling a trailer.
Various back pressure reducers have been developed to increase the efficiency and power of internal combustion engines. For example, U.S. Pat. Nos. 4,335,575 and 3,045,421 disclose exhaust back pressure reducers comprising a venturi throat that takes advantage of air flow over a moving vehicle. U.S. Pat. No. 2,500,510 discloses an exhaust pressure reducer comprising a "box-like vacuum chamber" having an opening at its front wall for an engine exhaust pipe (col. 1, lns. 39-45). Air flow over the moving vehicle is deflected downwardly under the vacuum chamber by an angular baffle plate, thereby creating suction therein for reducing back pressure (col. 2, lns. 13-27).
While utilizing the venturi effect to improve efficiency of an engine is desirable, the particular designs described above do not take advantage of various features of truck tractors (semi tractors), such as a low pressure zone created by air deflectors typically installed on such tractors.